It is proposed that there is an unmet need to define standards of care for radiology diagnosis. This need arises from questions which concern maintenance of optimal quality, reasonable accessibility and justifiable cost for radiology services in the face of increasing utilization and growing complexity of radiology procedures. A methodology has been developed by the American College of Radiology for accessing patterns of diagnostic efficacy seen from the viewpoint of the referring physician. The most numerous and costly radiologic procedures are of interest and will be represented with respect to typical medical problems and settings in a program of data collecting and processing. The principal products of this program will be handbooks which summarize for each procedure the attributes and manifestations of disease associated with all radiologic diagnostic outcomes, and with the "radiologic efficacy", the degree to which each referring physician is guided toward his definitive diagnosis by each procedure. Such compilations are expected to form the foundation for standards against which the judgments of referring physicians can be measured as they select radiographic procedures for their patients.